The present disclosure relates to increasing standby time in Code Division Multiple Access (CDMA) mobile stations.
The CDMA paging channel transmitted by the base station is divided into slots. A mobile station operating in the “slotted” mode only needs to monitor its own slot for messages. It may “sleep” at other times in order to increase standby time. When the mobile station is not engaged in a call, i.e. it is in an idle period, the mobile does not continuously monitor the paging channel but often remains in a low-power state. The mobile station shuts off all non-essential circuitry during idle periods between paging channel slot cycles. These low-power idle periods conserve power and prolong battery life. However, the mobile station needs to maintain system time during sleep intervals to determine when to wake up and listen to the paging channel again.
Prior to entry into the low-power sleep mode, the CDMA mobile station calculates in advance the timing required to wake up selected portions of the mobile station circuitry. The mobile station enters the low-power sleep mode for a time duration that is based on sleep timer periods, which is synchronized to the system time. In the sleep mode, the mobile uses a sleep timer to estimate the system time. The sleep timer is synchronized to the received pseudo-random noise (PN) sequence roll boundaries and to a roll count. The roll boundary occurs every 26⅔ mS. When the sleep timer matches the stored wakeup time, the mobile reactivates the selected portions of the mobile station circuitry to exit the sleep mode and reacquire communication with the system. Since synchronization is performed at the PN roll boundaries, the above configuration requires the mobile station to wait for one or more roll boundaries to occur before entering the sleep mode.